U.S. patent number 4,086,701 [Application Number 05/674,688] was granted by the patent office on 1978-05-02 for device for implanting an artificial endosseous element of ceramics and an implant method for use of the same.
This patent grant is currently assigned to Kyoto Ceramic Kabushiki Kaisha. Invention is credited to Masaya Hirabayashi, Haruyuki Kawahara.
United States Patent |
4,086,701 |
Kawahara , et al. |
May 2, 1978 |
Device for implanting an artificial endosseous element of ceramics
and an implant method for use of the same
Abstract
This invention is directed to a device for implanting an
artificial endosseous element of ceramics in the field of
dentistry, oral surgery and orthopedics, comprising an implant
screw pin and a flange member or flange members. The present
invention provides an implant element which is adapted for uses of
prosthesis even in cases where a hole remains after extraction of a
tooth or the bone tissues are unhealthy, and presents an implant
pin which is adapted to be securely held by means of the flange
member to the tissue of the jaw bone. This invention is also
directed to an implant method for use of such device.
Inventors: |
Kawahara; Haruyuki (Moriguchi,
JA), Hirabayashi; Masaya (Yokaichi, JA) |
Assignee: |
Kyoto Ceramic Kabushiki Kaisha
(Kyoto, JA)
|
Family
ID: |
26382394 |
Appl.
No.: |
05/674,688 |
Filed: |
April 7, 1976 |
Foreign Application Priority Data
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Apr 7, 1975 [JA] |
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50-42664 |
Apr 16, 1975 [JA] |
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50-46814 |
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Current U.S.
Class: |
433/174 |
Current CPC
Class: |
A61C
8/00 (20130101); A61C 8/0012 (20130101); A61C
8/0022 (20130101) |
Current International
Class: |
A61C
8/00 (20060101); A61C 013/22 () |
Field of
Search: |
;32/1A |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1,075,793 |
|
Feb 1960 |
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DT |
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2,401,323 |
|
Jul 1974 |
|
DT |
|
1,083,769 |
|
Mar 1965 |
|
UK |
|
Primary Examiner: Peshock; Robert
Attorney, Agent or Firm: Spensley, Horn & Lubitz
Claims
What is claimed is:
1. A device for implanting an artificial endosseous element into a
bone tissue consisting of:
an implant screw pin;
a flange member in combination with said pin for securely holding
said pin, said pin having external threads on the circumference of
a main portion thereof to be screwed directly into the bone tissue,
said main portion is adapted to be a main screw portion and being
provided with a tool-attaching portion at the top of said main
portion;
said flange member being of burnt ceramics and being anchored in
association with said pin into a facing shoulder recessed around
said pin, said facing shoulder is predeterminately provided in a
hard tissue of the bone, thereby holding said pin tightly in said
bone tissue.
2. The device according to claim 1 wherein washer-like flange
members are coupled to said flange member, said washer-like flange
members being of a generally cylindrical and tapered shape and
having an insert hole at the center thereof for fixing to said
implant pin.
3. The device according to claim 1 wherein a horizontal flange
member integral with said pin is adapted for said flange
member.
4. The device according to claim 2 wherein said washer-like flange
member has a plurality of significant openings of 0.2 - 0.7 mm and
preferably 0.3 - 0.5 mm of opening diameter at the surface
contacting with the bone tissue enabling penetration of newly grown
bone tissue through said flange member and numerous air passages
providing link with said significant openings.
5. The device according to claim 3 wherein said implant pin is
fabricated by mono-crystalline alumina ceramics.
6. A method of implanting an artificial endosseous element into a
bone structure of a human body for restoring said bone structure to
its original configuration consisting of:
incising a gingival tissue;
recessing a facing shoulder to receive flange member at a hard
tissue of said bone structure;
forming a tapered hole at the center of said facing shoulder in
said bone structure;
screwing into said tapered hole a ceramic implant screw pin having
external threads on a main portion thereof; and
screwing onto said screw pin a ceramic washer-like flange member
formed separate from said pin and having an insert hole provided
with threads corresponding to the external threads of said pin in
association therewith such that said flange member is anchored into
said facing shoulder thereby tightly holding said pin in said bone
structure.
7. A device for implanting an artificial endosseous element into a
bone structure of a human body for restoring said bone structure to
its original configuration consisting of:
an implant screw pin of ceramics;
a ceramic flange member in combination with said pin for securely
holding said pin; and
a ceramic nut element,
said implant pin having external threads on the circumference of a
main portion thereof to be screwed directly into bone tissue, which
main portion is adapted to be a main screw portion and external
threads on the circumference of a protruded portion to be protruded
from the upper surface of said bone tissue, which protruded portion
is adapted, when said pin is screwed in the bone, to be screwed
with said nut element, said protruded portion being provided with a
tool-attaching portion at the top thereof,
said flange member being anchored in association with said pin into
a facing shoulder recessed aorund said pin, which facing shoulder
is predeterminately provided in a hard tissue of the bone, and
said nut element being screwed onto said protruded portion of said
pin when said implant pin and said flange member are
associated.
8. A device for implanting an artificial endosseous element into a
bone structure of a human body for restoring said bone structure to
its original configuration consisting of:
an implant screw pin of ceramics; and
a ceramic washer-like flange member in combination with said pin
but fabricated separate therefrom,
said implant pin having external threads on the circumference of a
main portion thereof to be screwed directly into bone tissue, which
main portion is adapted to be a main screw portion, a
tool-attaching portion at the upper portion of said main portion
and a disk-shaped horizontal flange member which is projectably
formed horizontally outward on the border circumferences of said
main portion and said tool-attaching portion, which disk-shaped
horizontal flange member being integral with said main portion and
said tool-attaching portion,
said washer-like flange member being of reversed truncated cone
tapered with respect to the lower direction thereof, having an
insert hole provided with threads at the center of said flange
member for screwing with said pin and tool-attaching slots for
rotating said washer-like flange member and being anchored in
association with said pin, when said implant pin is screwed in the
bone, into a deep facing shoulder of smaller diameter which is
predeterminately provided at the hard tissue of the bone, and
said horizontal flange member being anchored into a shallow facing
shoulder of larger diameter so that the lower surface of said
horizontal flange member is in close contact with the upper surface
of said washer-like flange member.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for implanting an
artificial endosseous element of ceramics in the field of
dentistry, oral surgery and orthopedics, and to a method of
implanting the same.
2. Prior Art
In accordance with recent trends of development of bio-engineering,
implantation of artificial bio material into the bone tissue of a
living body has become popular. For instance, a dental implantation
technique has been developed, wherein in order to compensate for
the loss of natural teeth, an artificial tooth or implant is
implanted or inserted into the endosseous or subperiosteal portion
of the jaw as a substitute for a clasp abutment tooth of a
cantilevered bridge or an abutment tooth of a fixed bridge. The
artificial tooth or teeth thus implanted by the implantation
technique is called an implant crown, an implant bridge, or an
implant denture.
As for the type of endosseous implant in the field of dentistry and
oral surgery, the pin, blade and screw varieties are well
known.
As for the material of implant, compared with the conventional
metal materials such as Co-Cr alloy, Ni-Cr alloy and Ti, ceramics
have excellent compatibility with the surrounding tissues and also
are quite stable biologically as well as physically and chemically.
Thus, ceramics are considered the best material for implant
material. However, ceramic implants of the prior art are likely to
be damaged by biting stress since these ceramic implants are not
known for being mechanically strong and durable compared with those
made with metal. More specifically, in an implant in the field of
dentistry, compensation for the loss of natural teeth is
facilitated by screwing a screw-type implant in the endosseous or
subperiosteal portion of the jaw and fixing an artificial tooth to
the upper portion of the implant pin wherein the implant pin is
implanted in the jaw bone only by the screwing connection between
the implant pin and the jaw bone. The lower main portion of the
implant pin is screwed into the soft tissue of the jaw bone such
that due to the loose screw relation thereinbetween, the connecting
relation between the implant pin and the jaw bone may become loose
when repeated biting stresses are imparted thereto resulting in
instability of the implant pin. Instability of the implant pin may
destroy the entire device and prevent the growth of the surrounding
tissue and may also cause atrophy. A pocket (p) may become enlarged
as a result of the bone atrophy, whereupon the implant screw pin
becomes more unstable even to the point of causing the implant
screw pin to drop out thus reducing the pocket (p) to a nest of
bacilli. Another problem of conventional implants is that there
exists a constructional problem in that the screw of the implant
pin must be supportable against the external forces as well as be a
connecting medium connecting the implant pin with the bone tissue.
Given this wide scope of consideration, in order to obtain an
implant pin which is universal, the design of the screw of the
implant pin such as the outer diameter of the screw, pitch of the
threads of the screw and the length thereof are critical. This
holds true not only in the implant in the dental field but also to
that in oral surgical field.
One solution to the above problem is described in a previously
filed application, U.S. Ser. No. 550,186 filed on Feb. 18, 1975 and
now Pat. No. 4,016,651 issued Apr. 12, 1977, in which one means to
solve the above-described problem is provided. The present
invention is a further improvement thereon. In the previous
invention, a ceramic implant pin which has a main screw portion to
be screwed into the jaw bone and a protruded screw portion which
protrudes above the jaw bone from the upper surface of the hard
tissue is disclosed. In this device, both screw portions are
integrally connected with threads provided on the external
circumferences thereof. In addition, a ceramic nut element is
screwed into the protruded screw portion until the underside of the
nut element is pressed into contact with the surface of the hard
tissue of the jaw so that the tight screwing relationship between
the implant pin and the hard tissue (jaw bone) can be maintained by
tightening the nut element. Accordingly, this previous invention
discloses an endosseous implant pin and the technique of
implantation by which stability of the implant pin to the biting
stress is achieved.
The technique relevant to the prior art is adapted to tightly
connect the underside of the nut element to the jaw bone and
particularly to the upper surface of the hard tissue. In this
technique, the jaw bone functions effectively as a support base to
the nut element when the jaw bone is fresh and healthy and good
growth of the bone can be expected. However, if the bone tissue is
infected by bacilli or bone atrophy, the jaw bone does not function
as an effective support base and growth of the bone cannot be
expected. In such cases, in prosthesis by use of the implant of the
previous invention, boring processes should be required for the jaw
until fresh and healthy bone tissue appears by removing unhealthy
bone tissue. Unfortunately, due to a hollow formed by the boring
process, an implant pin implanted into the jaw bone may become
unstable because it is not supportable and so the implant of the
previous invention cannot be used when such a situation is
presented. This also holds true in the case where the implant pin
is implanted for a patient after extraction of a tooth since the
extraction hole remains in the jaw bone.
BRIEF SUMMARY OF THE INVENTION
Therefore, the present invention has the objects similar to those
of the prior invention but aims to provide an implant element which
is able to act as a prothesis even in cases where an extraction
hole remains after extraction of a tooth or because of a hole
created due to unhealthy bone tissues.
Therefore, one of the objects of the present invention is to
provide an implant element which is excellent in stability to the
biting stresses.
Another object of the present invention is to provide an implant
element of easy implantation techniques.
Still another object of the present invention is to provide an
implant element in which growth of the surrounding tissues after
implantation is excellent and does away with pocket formations.
Yet still another object of the present invention is to provide an
implant element which is endurable for a long period of time.
A further object of the present invention is to provide an implant
element which can be implanted immediately after extraction of a
tooth without the need for awaiting restoration of the surrounding
tissues.
A still further object of the present invention is to provide an
implant element which can be implanted even if the bone tissues are
infected by bacilli or there exists unhealthy bone tissue by the
proceeding atrophy.
These and other objects and advantages will become more apparent
from the following description of the invention by way of the
preferred embodiments .
BRIEF DESCRIPTION OF THE DRAWINGS
Four preferred embodiments with the examples of the implant in the
field of dentistry of the invention are described hereinafter with
reference to the accompanying drawings in which:
FIGS. 1 and 2 show the first embodiment of the invention wherein
FIG. 1(a) is a perspective view of an implant element comprising a
screw-type implant pin, and FIG. 1(b) is a perspective view of a
nut element used in combination with the implant device;
FIG. 2 is a longitudinal cross-section showing the prosthesis of an
artificial tooth using the implant element shown in FIG. 1;
FIGS. 3 and 4 show the second embodiment of the present invention
wherein FIG. 3 is a perspective view of another screw-type implant
pin and two larger and smaller washer-like flange members;
FIG. 4 is a longitudinal front view showing the prosthesis of the
present invention in using the implant element shown in FIG. 3;
FIGS. 5 and 6 show the third embodiment of the present invention
wherein FIG. 5 is a perspective view of an implant element which
has an integrally mounted flange element,
FIG. 6 is a longitudinal front view showing the use of the implant
element of FIG. 5; and
FIG. 7 shows the fourth embodiment of the present invention wherein
a longitudinal front view showing the prosthesis of the present
invention in using the washer-like flange member of FIG. 1(a) and
the implant element of FIG. 5.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
As is apparent from FIGS. 1 and 2, the first embodiment of the
present invention shows a screw implant pin (i.sub.1) provided with
an external screw-type configuration 1 in which a portion 11
(hereinafter referred to as the main screw portion) is adapted to
be screwed into the jaw bone (b) and in which a portion 12
(hereinafter referred to as the protruded screw portion) is adapted
to be protruded from the upper surface of the jaw bone (b) wherein
the pin (i) is screwed into the bone. The portions 11 and 12 are
generally formed simultaneously by a single screw thread. Numeral 2
denotes a wrench-attaching portion of a hexagonal pillar shape
formed at the top of the implant pin (i.sub.1).
A washer-like flange member (r.sub.1) is adapted as a support base
of the above-described implant pin (i.sub.1), which washer-like
flange member (r.sub.1) being a reversed truncated cone tapered
with respect to the lower direction. The cone has an insert hole 3
at the center thereof for securing it to the implant pin (i.sub.1).
On the inner wall of the insert hole 3, threads 31 are provided,
which threads correspond with those of the main screw portion 11 of
the implant pin (i.sub.1). In addition, the washer-like flange
member (r.sub.1) is provided with a screwdriver fixing slot members
4 for rotating the flange member.
The nut element (n) shown in FIG. 1(b) is screwed onto the
protruded screw portion 12 of the implant pin (i) and an artificial
tooth is adapted to be fixed to the upper portion of the nut
element (n). In FIG. 1(b), the nut element (n), the periphery of
which is truncated so as to form a hexagonal pyramid type
structure, is tapered in a downward and lower direction. This is
for the purpose of enabling easy operation in pressing or striking
the artificial tooth in order to fix it to the upper portion of the
nut element (n).
The configuration of the present invention with respect to a jaw is
described with reference to FIG. 2. In this figure, an artificial
tooth (t) is disposed about the implant pin (i.sub.1) and a
washer-like flange member (r.sub.1) is shown as being inserted into
the jaw member (b). At first, a gingival tissue (f) of a tooth
extraction section is incised. A hollow 5 is then made by a boring
process to the circumferential portion of a tooth extraction hole
(not shown) in the jaw bone (only a hard tissue (b.sub.1) in the
case of the exemplified drawing). The hollow 5 is tapered with
respect to the lower direction in correspondence with the
circumference of the washer-like flange member (r.sub.1). A tapered
hole 6 is axially disposed in the hollow 5 to correspond with the
main screw portion 11 such that the screw portion may be screwed
into the bone of the implant pin (i.sub.1) at the center of the
hollow 5.
Thereafter, a wrench is fitted into the wrench-attaching portion 2
of the implant pin (i.sub.1) to rotate it in order to implant the
implant pin (i.sub.1) into the jaw bone (b). In this manner, the
lower end of the screw portion 11 may reach a hard tissue (b.sub.3)
at the lower side of the jaw bone, while the upper portion of the
pin (i.sub.1), namely, a protruded screw portion 12, may be left
protruding from the upper surface of the jaw bone so as to be
susceptible to the nut element (n).
Then, the washer-like flange member (r.sub.1) is fixed so as to
proceed upward from the implant pin (i.sub.1) by rotating the
screwdriver fixed to the screwdriver-fixing slots 4. Thus, the
washer-like flange member (r.sub.1) is fixed tightly in the hollow
5 in the hard tissue (b.sub.1) of the jaw bone. At this stage, the
washer-like flange member (r.sub.1) is tightened even after the
circumference thereof come into contact with the inner wall of the
hollow 5 whereby the implant pin (i.sub.1) screwed in the jaw bone
(b, b.sub.2 and b.sub.3) is pulled upward by the proceeding of the
threads of the washer-like flange member (r.sub.1). This results in
the male threads of the main screw portion 11 and the female
threads of the tapered hole 6 to be tightly abutted whereby the
implant pin (i.sub.1) and the jaw bone (b, b.sub.2 and b.sub.3) can
maintain a tight screw relationship thus removing the unstable
tendency of the implant pin (i.sub.1). After this is achieved, the
nut element (n) is screwed onto the protruded screw portion 12 of
the implant pin (i.sub.1). At this stage, the nut (n) is tightened
a little more even after the lower side (base portion) of the nut
element (n) is brought into contact with the upper side of the
washer-like flange member (r.sub.1), whereby the implant pin (i) is
moved so as to maintain further tight screwing relationship with
the jaw bone. This is done such that the washer-like flange member
(r.sub.1), the nut element (n), and the implant pin (i) come into a
double locked relationship. After that, the artificial tooth (t) is
fixed to the upper portion of the nut element (n). In this
configuration, in order to restrict the rotation of the nut element
(n) and to enable synthetic connection of the nut element (n) with
the artificial tooth (t), an adhesive compound 7 such as cement and
amalgam is interposed between a fixed hole (t.sub.1) which is
grooved in a gingival portion (t.sub.1) of the artificial tooth (t)
and the top portion of the nut element (n). Thus, the artificial
tooth (t) is fixedly secured so as to extend upward from the nut
element (n). In this case, it is preferable to put some of the
above-mentioned adhesive compound 7 in the inner hollow 8 without
leaving any voids or vacancies. By restricting the rotation of the
nut element (n) with the adhesive compound 7, the washer-like
flange member (r.sub.1) is also restricted in its rotation because
of its engagement by the lower side of the nut element (n). Thus,
the prosthesis using the present invention has been described as
well as its method of insertion.
As for the most preferable example of the washer-like flange member
(r.sub.1), a reversed truncated cone body is used. This is one in
which the tapering is shown as in FIG. 1(b) from the top thereof
where it is smaller than the bottom thereof. However, it is to be
understood that other configurations such as a cylindrical body are
also applicable. However, it should be noted that the nut should
never be inserted such that the section that extends outward is
larger of the area since, in the case of of the washer-like flange
member (r.sub.1), the hollow 5 is formed so as to be also tapered
with respect to the lower direction in correspondence with the
flange member whereby the washer-like flange member (r.sub.1) is
held is position. Reversal of the flange member would not enable
such securement thereto. In the case of the washer-like flange
member of truncated cone tapered with respect to the upward
direction, the hollow 5 is formed also tapered with respect to the
upward direction in correspondence to the flange member, wherein
the washer-like flange member may be rendered slidable down toward
the soft tissue (b.sub.2) by the pressing force as applied from
above. Of course, threads 31 are provided for the insert hole 3 of
the washer-like flange member (r.sub.1) and thus the screwing of
the threads 31 with the main screw portion 11 of the implant pin
(i.sub.1) causes the sliding down action of the washer-like flange
member (r.sub.1) to be prevented at least to some degree. However,
as shown in FIG. 2, in the case of the washer-like flange member of
reversed truncated cone, the circumference of the washer-like
flange member (r.sub.1) is held by the cupshaped hollow 5 removing
the possibility of any sliding down action so that the threads 31
are not required to be provided at the insert hole 3 of the
washer-like flange member. In the case of the cylindrical
washer-like flange member, the flange member (r.sub.1) is not as
effectively held in the hollow 5 of the jaw bone (b) as compared
with the case of the washer-like flange member of reversed
truncated cone. However, even if the reversed truncated cone is
used, the sliding down action is minimal. In such a case, the
threads 31 are preferably provided at the insert hole 3. The insert
hole 3 of the washer-like flange member is required to be provided
at the center thereof. If the insert hole 3 is provided eccentric,
remote from the center, the implant pin (i.sub.1) cannot be
maintained in a stabilized manner since strain is produced in
screwing the washer-like flange member (r.sub.1) over the implant
pin (i.sub.1).
The second embodiment is shown with reference to FIG. 3 which takes
the example of the most typical dental endosseous implant and shows
the adoption of the present invention to the situation where the
soft tissue (b.sub.2) of the jaw bone (b) is partially infected.
The difference of the second embodiment from the first embodiment
resides in that the wrench-attaching portion 2 at the top of the
implant pin 12 is elongated, and the wrench-attaching member 2 is
directly connected to the artificial tooth (t) by means of the
adhesive compound 7 without using the nut element (n). Therefore,
only the main screw portion 11 is threaded on the circumference of
the screw 1 of the implant pin (i.sub.2). Furthermore, in place of
one washer-like flange member (r.sub.1) of reversed truncated cone
in the first embodiment, two larger and smaller washer-like flange
members (r.sub.2 and r.sub.3) are adopted. Similar to the
washer-like flange member (r.sub.1), the larger and smaller
washer-like flange members (r.sub.2 and r.sub.3) are constructed
such that at the center of ceramic disks, with the circumferences
thereof tapered with respect to the lower direction respectively,
form implant pin insert holes 3 and screwdriverfixing slots 4.
However, unlike the washer-like flange member (r.sub.1), threads 31
are not formed on the inner wall of the insert holes 3. The implant
pin (i.sub.2) is penetrated so as to be fixed through the two
washer-like flange members (r.sub.2 and r.sub.3) in such a manner
that the washer-like flange member (r.sub.3) of smaller diameter is
tightly fixed at the bottom of the hollow 5 of the jaw bone (b,
b.sub.1 and b.sub.2), and the washer-like flange member (r.sub.2)
of larger diameter is tightly fixed at the top of the hollow 5. In
this case, a clearance 9 is formed between the washer-like flange
members (r.sub.2 and r.sub.3) and the implant pin (i.sub.2). To the
hollow 5 is applied a boring process which proceeds until a healthy
bone tissue is reached. Owing to the growth operation of the
healthy bone tissue, the clearance 9 is filled in postoperation so
that the clearance 9 does not inconvenience operation; rather the
clearance works to securely stabilize the washer-like flange
members (r.sub.2 and r.sub.3).
In the third embodiment shown in FIGS. 5 and 6, a screw-type
implant pin (i.sub.3) is provided, similar to the implant pin
(i.sub.2) of the second embodiment, on the external circumference
thereof, with the screw 1 having the main screw portion 11 threaded
and the wrench-attaching portion 2. However, it is different from
the implant pin (i.sub.1) (i.sub.2) of the first and second
embodiments in that in this embodiment, a disk-like flange member
(r.sub.4) for securing the pin is formed horizontally outward on
the border circumferences of the screw 1 and the wrench-attaching
portion 2, and the flange member (r.sub.4) is predeterminately
provided integrally with the main portion 11 and the
wrench-attaching portion 2. The conditions of prosthesis using the
implant pin (i.sub.3) is shown in FIG. 6. As shown in FIG. 6, the
implant pin (i.sub.3) is adapted to be inserted into the jaw bone
(b) such that, when the implant pin (i.sub.3) is screwed in the
bone, the flange member (r.sub.4) may be tightly fixed in a facing
shoulder 51 which is grooved in the hard tissue (b.sub.1). In this
manner the flange member (r.sub.4) functions as a stable base for
the implant pin (i.sub.3) preventing its unstable tendency.
The fourth embodiment as shown in FIG. 7 shows prosthesis
conditions using the washer-like flange member (r.sub.1) of FIG.
1(a) and the implant pin (i.sub.3) of FIG. 5. As described
hereinabove, in cases where the bone tissues of both the tooth and
the jaw bone are infected by bacilli or atrophy, the affected part
should be fitted with a boring process up to the bone tissues. A
prosthesis condition which enables stable implantation is required
even if there exists a hollow formed by the abovementioned boring
process. FIG. 7 shows the example of utilizing the present
invention for such prosthesis. What is different in this embodiment
from the prosthesis condition shown in FIG. 6 is that the
washer-like flange member (r.sub.1) of reversed truncated cone
closely contact the hollow 5 which is smaller in diameter than that
of the facing shoulder 51 of the hard tissue (b.sub.1). The hollow
5 is disposed deeply in the upper portion of the soft tissue
(b.sub.2), and the washer-like flange member (r.sub.1) is also
interposed so that the upper surface thereof corresponds to the
lower surface of the facing shoulder 51. The implant pin (i.sub.3)
of FIG. 5 is screwed into the insert hole 3 having internal threads
31 and the tapered hole 6 pierced at the center of the washer-like
flange member (r.sub.1) until the flange member (r.sub.4) comes
into close contact with the lower surface of the facing shoulder 51
and the upper surface of the washer-like flange member (r.sub.1) to
be implanted. Also in the embodiment of FIG. 7, similar to the
embodiment of FIG. 6, the implant pin (i.sub.3) is stably secured
by the flange member (r.sub.4) and further by the washer-like
flange member (r.sub.1).
As for the material of the implant pin (i), the flange member (r)
and the nut element (n), ceramic compositions of matter have better
compatibility with the tissues of a living body and also are
nontoxic (metal may be toxic) and thus are preferred. However,
among ceramic compositions of matter, alumina ceramics is the most
preferable. Alumina ceramics has excellent mechanical strength to
withstand compression, bending, tensile stresses and impact, and is
substantially resistant to the above-mentioned external forces,
which is required of the implant element. Thus, Thus, the implant
element of alumina ceramics has strong durability with respect to
the biting stress and at the same time is physically, chemically
and biologically stable. Furthermore, in order to obtain clear
opaque images on radiography, the implant pin of alumina ceramics
which contains a little bit of more than one metal oxides such as
ZrO.sub.2, La.sub.2 O.sub.3 and Y.sub.2 O.sub.3 has advantageous
clinical effect. With respect to the alumina ceramics compositions
of matter, prior U.S. Patent Application Ser. No. 524,557 filed on
Nov. 18, 1974, may be referred to and is herein incorporated by
reference.
Further, the implant pin (i) fabricated by monocrystalline alumina
ceramics has high strength to the biting stress and is preferable.
In the case where the implant pin (i.sub.3) is provided integrally
with the flange member (r.sub.4), the implant pin (i.sub.3) and the
flange member (r.sub.4) are fabricated by the same material.
However, in the case where the washer-like flange members (r.sub.1,
r.sub.2 and r.sub.3) are fabricated separately from the implant pin
(i), the flange members (r.sub.1, r.sub.2 and r.sub.3) are
preferably fabricated by porous alumina ceramics. This is because
the flange member of fine ceramics of impermiability has further
compatibility with the bone tissues compared with other material
such as metal and plastic, and easy growth of the bone tissue on
the surfaces of the washer-like flange members (r.sub.1, r.sub.2
and r.sub.3) is expected. However, the newly grown bone tissues
cannot penetrate through the inner portions of the flange members
to be secured. On the other hand, the flange members (r.sub.1,
r.sub.2 and r.sub.3) of porous material which contacts with the
surface of the bone tissue does permit the penetration of newly
grown bone tissues through the hollows of the flange members
(r.sub.1, r.sub.2 and r.sub.3) easily enabling complex material or
synthetic body and living body to be formed between the tissues and
the flange members (r.sub.1, r.sub.2 and r.sub.3) resulting in
further stable securing of the flange members (r.sub.1, r.sub.2 and
r.sub.3). In order to enable penetration of newly grown bone
tissues, the present inventors found that the washer-like flange
members (r.sub.1, r.sub.2 and r.sub.3) of porous ventilative
ceramics having significant openings of 0.2 - 0.7 mm and preferably
0.3 - 0.5 mm of opening diameter at the contact surface with the
bone tissue and formed with numerous air passages linked with the
significant openings are the most preferable. The ventilative
feature is required for dispersing gases (CO.sub.2 and NH.sub.3 are
especially abundant in a living body) which exist innerly in
correspondence with the penetration of newly grown bone tissue to
the significant openings. By the ventilative feature, the
penetration of the newly grown bone tissues to the surfaces of the
washer-like flange members (r.sub.1, r.sub.2 and r.sub.3) is
further promoted. Of course, the whole of the washer-like flange
members (r.sub.1, r.sub.2 and r.sub.3) may be of porous material
and in consideration of mechanical strength, the flange members
(r.sub.1, r.sub.2 and r.sub.3) may be constructed such that some
range of thickness at the surface which is to contact with the bone
tissue is porous and the range of thickness inner than the surface
is non-porous.
With respect to details of the porous alumina ceramics and the
manner of manufacture thereof, U.S. Patent Application filed on
Apr. 4, 1975, entitled "Ceramic Endosseous Implant Element Having
Porous Contacting Surface and the Method of Manufacturing It" of
the same applicant may be referred and is herein incorporated by
reference.
The present invention is described hereinabove by way of the
preferred embodiments. As already described, the present invention
presents an implant pin which is adapted to be securely held by
means of the flange member (r) which is tightly fixed, under the
conditions of the implant pin (i) screwed in the bone, in the
hollow 5 or the facing shoulder 51 provided at the hard tissue
(b.sub.1) of the jaw bone. In this manner, the biting stress or
other external forces imparted to the implant pin (i) afterwards
can be diverged mainly by the flange member (r) and the implant pin
(i) so that the external forces transmitted to the screw (i) is
reduced. This means that any unstable tendency and damage of the
implant pin (i) after operation can be prevented. Moreover, due to
the fact that the implant (i) is stably secured, good growth of the
surrounding bone tissues of the implant (i) is expected, bone
atrophy does not occur, the implant (i) may not be loose or dropped
off, and a pocket of a nest of bacilli is not produced.
Further, even if there exists a tooth extraction hole after
extraction of a tooth, or the jaw bone (b) is infected up to bone
tissues, boring process is given to the jaw bone (b) up to the
fresh and healthy bone tissue where, notwithstanding a hollow
produced by the boring process, the implant pin (i) can be
implanted to be stably secured in the jaw bone (b) according to the
first, second and fourth embodiments since the washer-like flange
members (r.sub.1, r.sub.2 and r.sub.3) are fixed tightly in the
hollow and can maintain fixture of the implant pin (i). Thus, as
compared with the prior art, the present invention can provide a
developed implant technique which can use the implant element of
the prior art even in such a case where a tooth extraction hole
exists or where the bone tissues of the jaw bone (b) are infected,
the implant element can be implanted without waiting for the
restoration of the surrounding tissues.
In addition, if the implant pin (i) is fabricated by
mono-crystalline alumina ceramics, resistance to the biting stress
is promoted and also if the washer-like flange members (r.sub.1,
r.sub.2 and r.sub.3) are fabricated by porous alumina ceramics,
penetration of the newly grown bone tissues is enabled through the
flange members (r.sub.1, r.sub.2 and r.sub.3) whereby the flange
members are further stably secured.
Further, in the case where the main screw portion 11 is provided
with threads 31 in the inner wall of the insert hole 3, the main
screw portion 11 of the implant pin (i) can still have tight
screwing relationship therewith. The implant pin (i) can be
securely implanted in the bone, and in addition, to the threads, as
with the prior invention. This is achieved by having a nut element
(n) screwed onto the protruded screw portion 12 at the upper
portion of the implant pin (i).
Also, as described hereinabove, the external forces imparted to the
screw 1 of the implant pin (i) can be reduced by the flange member
(r) so that the main screw portion 11 of the screw 1 need not be a
support medium to the external forces as well as a connecting
medium of the implant (i) with the bone tissues. The screw portion
only has to function as a connecting medium whereby such factors as
support to the external forces need not be required to be
considered in designing the pitch of threads, length of the screw,
or diameter of the screw and the like.
As for the material of the implant element in the present
invention, ceramics is used whereby even if the implant element is
left for a long time after implantation, the implant element has
good compatibility with the bone tissue and it is non-toxic so
that, together with the above-described durability, it can be used
semipermanently.
The present invention is herein described taking the example of
implant element in the dental field. However, the same advantages
of the present invention can be expected in the orthopedic field
such as in the treatment of fractured arm, legs and the like or
decay in joints. Thus, this invention should not be limited to the
dental field.
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